Method for producing metal dies or molds containing cooling channels by sintering powdered metals

ABSTRACT

A sintered metal die or mold having formed therein an internal channel for conducting a heat transfer medium therethrough, and a method for producing same. The method includes the steps of disposing sintering powder, such as iron, copper, tungsten carbide or titanium carbide, in a frame or box, about a pattern made of an infiltrant metal, such as copper, lead, cobalt, nickel, iron or alloys thereof, having a lower melting point than that of the sintering powder, the pattern corresponding in configuration to that of the cavity surface of the desired channel for the heat transfer medium and being positioned within the sintering powder in the position desired for the channel, heating the powder together with the pattern to sintering temperature, whereby to sinter the powder and infiltrate the infiltrant metal forming the pattern into the powder, and cooling so as to obtain a sintered metal die or mold having an internal channel whose configuration complements that of the pattern surface.

United States Patent [1 [111B 3,915,699

Umehara et al. *Oct. 28, 1975 METHOD FOR PRODUCING METAL DIES OR MOLDS CONTAINING COOLING [56] References: Cited- CHANNELS BY SINTERING POWDERED UNITED STATES PATENTS METALS 3,706,550 12/1972 Umehara et al. 75/200 [75] Inventors: Hanji Umehara; Takashi Kimura;

Hiroshi Hamamoto, all of Nagoya, Primary ExaminerBenjamin R. Padgett Japan Assistant Examiner-B. Hunt [73] Assignee: Kabushiki Kaisha Toyota Chuo Kenkyushoto, Japan ABSTRACT A sintered metal die or mold having formed therein an internal channel for conducting a heat transfer me- Ki g 1989 dium therethrough, and a method for producing same.

S een alme The method includes the steps of disposing sintering [22] Filed: Dec. 26, 1972 powder, such as iron, copper, tungsten carbide or titanium carbide, in a frame or box, about a attern made [211 App! 318l95 of an infiltrant metal, such as copper, lead, cobalt, [44] Published under the Trial Volunta P t t nickel, iron or alloys thereof, having a lower melting Program on January 28, 1975 as document no. point than that of the sintering powder, the pattern B 318,195. corresponding in configuration to that of the cavity Related US. Application Data surface of the desired channel for the heat transfer medium and being positioned within the sintering [63] Commuano of $4,335, Oct powder in the position desired for the channel, heating abandoned the powder together with the pattern to sintering temperature, whereby to sinter the powder and infiltrate Notice: The portion of the term of this [30] Foreign Apphcanon Pnonty Data the infiltrant metal forming the pattern into the pow- NOV. 8, Japan 44-89965 der and ooling so as to btain a Sintered meta] o mold having an internal channel whose configuration [52] US. Cl 75/208 R; 75/200; 75/214 Complements that f the pattern surface 51 Int. Ci. B22f 1 00; B22F 5/00 [58] Field of Search 75/214, 200, 208 R 12 Clam, 7 Draw"; Flgms 6. 3/ Ug nee/v Pod/0E FOR S/NTEQ/NG METHOD FOR PRODUCING METAL DIES OR MOLDS CONTAINING COOLING CHANNELS BY SINTERING POWDERED METALS This is a continuation of application Ser. No. 84,335, filed Oct. 27, 1970.

BACKGROUND OF THE INVENTION This invention relates to a sintered metal die or mold, such as a casting mold, a pressing die, or a die-cast mold, having formed therein an internal channel for conducting a heat transfer medium therethough, and to a method of producing same.

DESCRIPTION OF THE PRIOR ART The manufacture of products using a metal die or mold requires temperature control of the die or mold before and/or during processing, such as for heating, maintaining a constant temperature, rapid quenching, or slow cooling. It has hitherto been know to provide channels in the metal die or mold for conducting a heating or cooling medium therethrough for effecting such temperature control, by mechanically perforating the metal die or mold. However, since it is difficult or nearly impossible by this method to provide curved channels inside the actual die or mold along the mold surfaces, the channels formed in this manner have generally been linear and thus have had a low heat transfer efficiency. Accordingly, it has been conventional to provide pipes for passing a heating or cooling medium on the periphery of the metal die or mold to control the temperature by heat transfer between the pipe walls and the outside of the metal die or mold. This method, however, had the disadvantage that the thermal conductivity is very low and the desired temperature control is very difficult to obtain.

SUMMARY OF THE INVENTION The present invention provides for the manufacture of a metal die mold, having formed therein an internal channel for conducting a heat transfer medium therethough, by means of a sintering process which obviates the disadvantages of the conventional methods briefly outlined above. The channel formed by means of the present process can be of any desire shape and at any desired position in the metal mold or die and does not require any machining operations nor much time and expense.

The improved method comprises the steps of disposing sintering powder, such as iron, copper, tungsten carbide or titanium carbide, in a frame or box, about a pattern made of an infiltrant metal, such as copper, lead, cobalt, nickel, iron or alloys thereof, having a lower melting point than that of the sintering powder, the pattern corresponding in configuration with that of the cavity surface of the desired channel for conducting the heat transfer medium and being positioned within the sintering powder in the position desired for the channel, and heating the powder together with the pattern to sintering temperature. During the sintering operation, the infiltrant metal pattern melts and infiltrates entirely into the sintered metal powder. Upon cooling, the resultant product is hardened sintered mold or die having a cavity or channel having a shape and size corresponding to the surface of the pattern at the portion where the pattern was disposed. Furthermore, the infiltrated metal also serves to strengthen and reinforce the die or mold at the parts surrounding the channel, and

fully closes any small holes around the channel in the sintered material so that the cooling or heating medium flowing through the channel, even when under high pressure, will not enter into the metal die or mold, thereby rendering the die or mold capable of enduring long term use without leaking.

It will be apparent from the above that a primary object of the present invention is to provide a sintered metal die or mold having formed therein an internal channel for conducting a heat transfer medium therethrough, and a method for producing same.

Another object of the invention is to provide a method for producing a metal die or mold as described above, without machining.

Still another object of the invention is to provide a sintered metal die or mold as described above, having formed therein a curved internal channel for conducting a heat transfer medium therethrough.

A further object of the invention is to provide a sintered metal die or mold as described above, wherein the channel for conducting the heat transfer medium is relatively leakproof.

A still further object of the invention is to provide a method for producing a metal die or mold as described above, which is easy to follow, inexpensive, provides consistent results, and is commercially practicable.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims.

The invention itself, however, both as to its organization and its operation, together with additional objects and advantages thereof, will best be understood from the following description of the specific embodiments when read in connection with the accompanying drawings, wherein like reference characters indicate like parts throughout the several figures, and in which:

FIG. 1 is a cross-sectional view of a metal casting mold of sintered metal powder material and having formed therein an internal channel for conducting a heat-transfer medium therethrough;

FIG. 2 is a horizontal cross-sectional view taken along the line 2-2 of FIG. 1;.

FIG. 3 is a perspective view of a pattern used for forming the channel in the metal mold of FIGS. 1 and FIG. 4 is a perspective view of a mother mold for forming the mold surfaces of the metal mold of FIGS. land 2;

FIG. 5 is a cross-sectional view of the embodiment for producing the metal mold of FIGS. 1 and 2, showing metal powder having the pattern of FIG. 3 and the mother mold of FIG. 4 disposed therein;

FIG. 6 is a cross-sectional view taken along the line 6-6 of FIG. 5; and

FIG. 7 is a cross-sectional view taken along the line 77 of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS To make the invention more fully understood, a description will be made of an embodiment of the invention as applied to the manufacture of a casting mold containing channels for conducting a heat transfer medium through the mold.

As shown in FIGS. 1 and 2, the casting mold to be manufactured is of a split type which consists of a lower mold 721 and an upper mold 722 which are made of sintered iron powder material. The lower mold 721 has a lower mold surface 601, a zig-zag shaped internal channel 111 for conducting a heat transfer medium through the lower mold, and guide holes 766. The upper mold 722 has an upper mold surface 602, a down-gate 761, a tapping 762, a zig-zag shaped internal channel 121 for conducting a heat transfer medium through the upper mold similar to the channel 1 1 1, and guides 765. The channels 111 and 121 are provided at their open ends with threaded screw portions 115 and 116 to connect with an inlet pipe and outlet pipe, respectively, for a heat transfer medium, such as cooling water. With the upper mold 722 and lower mold 721 laid on one another, a cavity made by the mold surfaces 601 and 602 forms a casting mold surface of a dish-like cup having a flat bottom similar in shape to the cup portion 60 of the mother mold 6 shown in FIG. 4.

The pattern 11 for the formation of the channel 111 of the lower mold is shown in FIG. 3. The pattern 11 is made from copper, has a U-shaped zig-Zag form, and is provided at each end with threaded screw portions and 16 for the formation of threaded screw portions 115 and 116 of the channels. The mother mold 6 for the formation of the casting mold surfaces has, as shown in FIG. 4, a cup portion 60 having at its open edge a gate stick 61 for the formation of the down-gate 761 and a tapping bar 62 for forming the tapping 762.

The process of forming the casting mold of FIGS. 1 and 2 is illustrated in F IGS'. 5 to 7. A ceramic forming frame 31 having a bottom is coated with alumina powder as a demolding agent on the inner peripheral surface thereof. A layer of iron powder is then charged on the bottom of the forming frame 31. The pattern 11 shown in FIG. 3 is then disposed on the layer of iron powder over which additional iron powder is then charged. Upon these layers is then mounted a ceramic mother mold 6 coated with alumina powder over the entire surface. Additional iron powder is then charged to the level of the upper edge of the mother mold 6, thereby forming the lower layer 71. For the formation of the guide portions 765 and 766, ceramic mother molds 65 having a cup-like configuration in crosssection and coated with alumina powder over their entire surface, are then buried in the iron powder at positions in four radial directions of the mother mold 6 such that their upper ends are respectively located on the same level as the upper edge of the cup 60. On the lower layer 71 is then coated a layer 8 of alumina powder for the formation of a parting surface. The obtained surface is charged with additional iron powder, upon which is mounted within the mother mold 6 a copper pattern 21, similar to the pattern 11, having a zig-zag shape with its middle portion bent downward as shown in FIG. 3. Additional iron powder is then charged upon all these layers, thereby forming the upper layer 72.

A load of about 0.8 ton per square centimeter is then applied upon the upper layer 72 to compress the iron powder. The compressed iron powder compact within the forming frame 31 is then placed in a sintering furnace and sintered at 1 120C. for 60 minutes in an atmosphere of nitrogen.

Since the melting point of copper is 1083C and thus below the temperature used for sintering, the copper patterns 11 and 21 melt during the sintering operation. The molten copper infiltrates into the spaces in the sintered iron powder by a capillary action, thereby leaving cavities in the sintered material in the form of internal channels 111 and 121 corresponding in dimensions and shape to the patterns 11 and 21, respectively, at the portions where these patterns had been located. The infiltration of the molten copper into the sintered iron powder strengthens the binding of the iron powder around the channels 111 and 121 and also fully closes any small holes around the channels in the material so as to prevent leakage of any heat transfer medium from the channels into the mold when the mold is in use.

Following the sintering operation, the sintered product is then cooled and removed from the outer frame 31. The alumina powder parting agent prevents the upper charged layer 72 and the lower charged layer 71 from becoming sintered to each other, to the mother molds 6 and 65, or to the outer frame 31 during the sintering operation. Therefore the mother molds 6 and 65 may be readily removed, thereby resulting in the sintered metal casting mold shown in FIGS. 1 and 2, comprising a lower mold 721 having formed therein an internal channel 111, and an upper mold 722 having formed therein an internal channel 121. When the upper mold 722 is laid upon the lower mold 721, their meeting surfaces are snugly fitted to each other, thereby preventing any leaking of molten metal when they are used in manifacturing molded products.

In the embodiment described above, the mother molds 6 and 65 are made out of ceramic material, having a softening point much higher than the sintering temperature. Therefore no collapsing or deformation of the mother molds occur during the sintering operation, and these molds may be reused many times. However, instead of being made out of ceramic material, the mother molds 6 and 65 may be made of copper similar to the patterns 11 and 21. In that case the mother molds 6 and 65 would melt during the sintering ation and infiltrate into the spaces of the sintered iron powder, thereby strengthening and reinforcing the sintered product, and forming the mold surfaces 601 and 602, the down-gate 761, the tapping 762, the guides 765 and the guide holes 766 in a manner similar to the formation of the channels 111 and 121 as described above.

In the procedure above described, the iron powder is compressed prior to being sintered. This increases the density and strength of the final mold and also helps to prevent collapse of the iron powder surfaces at the portions in contact with the copper patterns 11 and 21 when the patterns melt and form cavities during the sintering operation. When it is desired to obtain a porous sintered material having a low density without excessively compressing the metal powder, a two-stage sintering process can advantageously be employed which includes a presintering for about 2 hours at 900C followed by the normal sintering operation for about 60 minutes at 1 C as above described. During the presintering operation the copper of the pattern will not melt but the iron powder will be sintered and there will be obtained a substantially skeleton-like material. Thereafter during the normal sintering operation, the infiltration of the copper and the normal sintering of the iron powder will occur. Consequently the infiltration is carried out smoothly and a more sturdy sintered material can be obtained.

In the method of manufacture according to this invention, when a forming box which can endure compression and sintering is used as a molding frame, as in the above-described embodiment, it is possible to sinter the metal powder within the forming frame. As a consequence, the metal powder before or while it is sintered is not subjected to collapsing. This is specifically advantageous when the metal powder is collapsible because it cannot be compressed or is low in compressibility. However, a molding frame may not always be required during the sintering operation. For example, a forming die can be used as a molding frame in which the metal powder, patterns for forming the channels, and mother molds for forming the mold surfaces, are disposed in an arrangement and compressed by the forming die. The resulting compact with the patterns and mother molds will be very sturdy and can be taken out of the die and sintered without a molding frame.

In carrying out the method of the present invention, the metal powder used as the sintering material may be iron, copper, tungsten carbide, titanium carbide or the like. The infiltrant metal used to form the pattern must have a melting point lower than the sintering temperature of the sintering material. The sintering conditions will, of course, vary with the particular materials used for the sintering material and for the pattern. For example, if a ferrous metal powder whose main ingredient is iron, or iron-carbon is used as the sintering powder, then the infiltrant metal used for forming the pattern should be either copper, a copper-manganese alloy or a copper-cobalt alloy, for example, a 95% copper 5% manganese alloy, a 97% copper-3% cobalt alloy, or the like. Typical sintering conditions for these materials would be 60 minutes at 1 120C in an atmosphere of nitrogen. If copper powder whose main ingredient is copper, or copper alloy, is used as the sintering powder, then the infiltrant metal used for forming the pattern should be lead, a lead-tin alloy or lead-cadmium alloy, for example, a 50% lead-50% tin alloy, an 82% lead- 18% cadmium alloy or the like, with typical sintering conditions being 60 minutes at 500C in an atmosphere of hydrogen. If a metal powder whose main ingredient is tungsten carbide is used as the sintering material, then the infiltrant metal used for forming the pattern should be cobalt, nickel, an iron alloy or the like, with typical sintering conditions being 60 minutes at l550C in an atmosphere of hydrogen. If a metal powder whose main ingredient is titanium carbide is employed as the sintering material, then the infiltrant metal used for forming the pattern should be nickel, a nickel molybdenum alloy for example, a 95% nickel-5% molybdenum alloy, a cobalt alloy or the like, with typical sintering conditions being 60 minutes at l550C in an atmosphere of hydrogen.

The patterns used in the present invention will have the same dimensions and shape as the channels desired to be formed in the die or mold. Furthermore, the channels may be located at any desired position within the die or mold merely by varying the position of the pattern within the sintering powder when the pattern and powder are charged into the frame.

As shown in the above-described embodiment, the molding surfaces of the metal die or mold are formed together with the formation of the sintered product with the channels. It is also possible, however, to first form the sintered material having the channels formed therein, and thereafter form the molding surfaces by cutting the sintered material.

The method of the present invention can be applied not only to the manufacture of casting molds as shown in the above-described embodiment, but also to the manufacture of press-dies, die-casting molds, molds for plastic, glass or rubber molding, and to any other metal molds in the broad sense.

Although certain specific embodiments of the invention have been shown and described, it is obvious that many modifications thereof are possible. The invention, therefore, is not intended to be restricted to the exact showing of the drawings, and description thereof, but is considered to include reasonable and obvious equivalents.

What is claimed is:

l. A method for producing a die or mold from sintered powder material and having at least one internal channel formed therein for conducting a heat transfer medium into, through, and out of the mold, comprising placing a first layer of sintering powder selected from the group consisting of iron, iron-carbon, copper, cop per alloy, tungsten carbide and. titanium carbide in a frame, forming a mother mold conforming in size and configuration to a desired mold cavity, forming a pattern of long and slender shape having a desired surface configuration corresponding to that of said internal channel for conducting a heat transfer medium and which complements the surface of the desired mold cavity, said pattern being made of metal infiltratable into the pores of said sintering powder and having a lower melting point than that of said sintering powder, at least partially embedding said mother mold in said layer of sintering powder, adding a second layer of said sintering powder to completely embed the mother mold and separated from the first layer by a demolding agent, completely embedding said pattern in complementary spaced relation in one of said layers of sintering powder so that both ends of said pattern contact with the inside of a wall of said frame, heating said sintering powder, mother mold and pattern to a sintering temperature to sinter said powder and to infiltrate said infiltratable metal of said pattern into said powder, and cooling so as to obtain a hardened, sintered mold separable into two parts along the boundary of said first and second layers and having an internal channel whose configuration complements that of said pattern and the mold cavity.

2. A method for producing a die or mold from sintered powder material in accordance with claim 1, wherein said mother mold is formed of a ceramic and is coated with a demolding agent prior to embedment.

3. A method for producing a die or mold from sintered powder material in accordance with claim 1, wherein said mother mold is formed of a metal infiltratable into the pores of said sintering powder and having a lower melting point than that of said sintering powder.

4. A method for producing a die or mold from sintered powder material according to claim 1, wherein said pattern is embedded in said first layer of sintering powder and a second and similar pattern is embedded in said second layer of sintering powder prior to said heating step to sintering temperature.

5. A method of producing a metal die or mold from sintered powder material according to claim 1, which further comprises removing said hardened and sintered die or mold from said frame after cooling.

6. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is presintered at a lower temperature than the melting temperature of the infiltratable metal forming said pattern before heating to sinter said sintering powder completely.

7. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is compressed before heating to sinter said powder.

8. A method for producing a die or mold from sintered powder material according to claim 7, wherein said compressed sintering powder together with said mother mold and pattern embedded therein are removed from said frame before heating to sinter said powder.

9. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is ferrous metal powder whose main ingredient is iron or iron-carbon and said pattern is made of a metal selected from the group consisting of copper, copper-manganese alloy, and copper-cobalt alloy.

10. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is copper powder whose main in gredient is copper or copper alloy, and said pattern is made of a metal selected from the group consisting of lead, lead-tin alloy, and lead-cadmium alloy.

11. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is carbide powder whose main ingredient is tungsten carbide and said pattern is made of a metal selected from the group consisting of cobalt, nickle, and iron alloy.

12. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is carbide powder whose main ingredient is titanium carbide and said pattern is made of a metal selected from the group consisting of nickel,

nickel-molybdenum alloy, and cobalt alloy. 

1. A METHOD FOR PRODUCING A DIE OR MOLD FROM SINTERED POWDER MATERIAL AND HAVING AT LEAST ONE INTERNAL CHANNEL FORMED THEREIN FOR CONDUCTING A HEAT TRANSFER MEDIUM INTO, THROUGH, AND OUT OF THE MOLD, COMPRISING PLACING A FIRST LAYER OF SINTERING POWDER SELECTED FROM THE GROUP CONSISTING OF IRON, IRON-CARBON, COPPER, COPPER ALLOY, TUNGSTEN CARBINDE AND TITANIUM CARBIDE IN A FRAME, FORMING A MOTHER MOLD CONFORMING IN SIZE AND CONFIGURATION TO A DESIRED MOLD CAVITY, FORMING A PATTERN OF LONG AND SLENDER SHAPE HAVING A DESIRED SURFACE CONFIGURATION CORRESPONDING TO THAT OF SAID INTERNAL CHANNEL FOR CONDUCTING A HEAT TRANSFER MEDIUM AND WHICH COMPLEMENTS THE SURFACE OF THE DESIRED MOLD CAVITY, SAID PATERN BEING MADE OF METAL INFILTRATABLE INTO THE PORES OF SAID SINTERING POWDER AND HAVING A LOWER MELTING POINT THAN THAT OF SAID SINTERING POWDER, AT LEAST PARTIALLY EMBEDDING SAID MOTHER MOLD IN SAID LAYER OF SINTERING POWDER, ADDING A SECOND LAYER OF SAID SINTERING POWDER TO COMPLETELY EMBED THE MOTHER MOLD AND SEPARATED FROM THE FIRST LAYER BY A DEMOLDING AGENT, COMPLETELY EMBEDDING SAID PATTERN IN COMPLEMENTARY SPACED RELATION IN ONE OF SAID LAYERS OF SINTERING POWDER SO THAT BOTH
 2. A method for producing a die or mold from sintered powder material in accordance with claim 1, wherein said mother mold is formed of a ceramic and is coated with a demolding agent prior to embedment.
 3. A method for producing a die or mold from sintered powder material in accordance with claim 1, wherein said mother mold is formed of a metal infiltratable into the pores of said sintering powder and having a lower melting point than that of said sintering powder.
 4. A METHOD FOR PORDUCING A DIE OR MOLD FROM SINTERED POWDER MATERIAL ACCORDING TO CLAIM 1, WHEREIN SAID PATTERN IS EMBEDED IN SAID FIRST LAYER OF SINTERING POWDER AND A SECOND AND SIMILAR PATTERN IS EMBEDED IN SAID SECOND LAYER OF SINTERING POWER PRIOR TO SAID HEATING STEP TO SINTERING TEMPERATURE.
 5. A method of producing a metal die or mold from sintered powder material according to claim 1, which further comprises removing said hardened and sintered die or mold from said frame after cooling.
 6. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is presintered at a lower temperature than the melting temperature of the infiltratable metal forming said pattern before heating to sinter said sintering powder completely.
 7. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is compressed before heating to sinter said powder.
 8. A method for producing a die or mold from sintered powder material according to claim 7, wherein said compressed sintering powder together with said mother mold and pattern embedded therein are removed from said frame before heating to sinter said powder.
 9. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is ferrous metal powder whose main ingredient is iron or iron-carbon and said pattern is made of a metal selected from the group consisting of copper, copper-manganese alloy, and copper-cobalt alloy.
 10. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is copper powder whose main ingredient is copper or copper alloy, and said pattern is made of a metal selected from the group consisting of lead, lead-tin alloy, and lead-cadmium alloy.
 11. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is carbide powder whose main ingredient is tungsten carbide and said pattern is made of a metal selected from the group consisting of cobalt, nickel, and iron alloy.
 12. A method for producing a die or mold from sintered powder material according to claim 1, wherein said sintering powder is carbide powder whose main ingredient is titanium carbide and said pattern is made of a metal selected from the group consisting of nickel, nickel-molybdenum alloy, and cobalt alloy. 